Sec Form 3 Filing - HONEYWELL INTERNATIONAL INC @ Quantinuum Inc. - 2026-06-04

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person HONEYWELL INTERNATIONAL INC 2. Issuer Name and Ticker or Trading Symbol Quantinuum Inc. [ QNT] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 855 S. MINT STREET, 3. Date of Earliest Transaction (MM/DD/YY) 06/04/2026 (Street) CHARLOTTE, NC28202 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class B Common Stock 124,628,729 I See Footnotes ( 1 ) ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Common Units ( 3 ) ( 3 ) ( 3 ) Class A Common Stock 124,628,729 I See Footnotes ( 1 ) ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other HONEYWELL INTERNATIONAL INC 855 S. MINT STREET CHARLOTTE, NC28202 X Honeywell Holdings International Inc. C/O HONEYWELL INTERNATIONAL INC. 855 S. MINT STREET CHARLOTTE, NC28202 X Signatures Honeywell International Inc., /s/ Jimmy Steinberg, Senior Vice President, Corporate Development and Global Head of M&A 06/04/2026 Signature of Reporting Person Date Honeywell Holdings International Inc., /s/ Jake Wasserman, Secretary 06/04/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes (i) 28,630,074 common units of Quantinuum Holdings, LLC ("Common Units") and a corresponding number of shares of Class B common stock of Quantinuum Inc. held directly by Honeywell Holdings International Inc. and (ii) 95,998,655 Common Units and a corresponding number of shares of Class B common stock of Quantinuum Inc. held directly by Honeywell International Inc. ("Honeywell"). ( 2 )Honeywell Holdings International Inc. is a wholly owned subsidiary of Honeywell, which is a publicly traded company with securities listed on The Nasdaq Stock Market LLC. ( 3 )Each Common Unit may be redeemed or exchanged for one share of Class A common stock of the Issuer (or, at the Issuer's election, cash). The Common Units have no expiration date. Upon the redemption or exchange of Common Units, a number of shares of Class B common stock equal to the number of Common Units that are redeemed or exchanged will automatically be cancelled for no consideration.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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